1. Field of the Invention
The present invention relates to an engine mounting for suspending an engine relative to a vehicle structure.
2. Description of the Prior Art
In an automotive vehicle, the elastic block structures employed for the suspension of an engine relative to the vehicle structure have a principal function to restrain low frequency vibrations falling within a vibration restrained domain. In this respect, the block structures must have a high dynamic spring constant (high stiffness) suitable for restraining such vibrations. Unfortunately, this high stiffness suitable for restraining such low frequency vibrations results in a considerable reduction in passenger comfort under the effect of high frequency vibrations falling within a vibration insulated domain.
The conventional elastic block structures are set to exhibit a characteristic as represented by a broken line curve as shown in FIG. 3. With the conventional engine mounting employing the elastic blocks, since the dynamic spring constant of the elastic blocks is set high enough to restrain or attenuate low frequency vibrations (between 5 and 30 Hz) produced by an uneven road surface or by engine idling upon its idling operation, the high frequency vibrations (above 30 Hz) due to engine operation above the idle speed are not insulated or filtered satisfactorily. On the other hand, if the dynamic spring constant is set high enough to insulate or filter the high frequency vibrations having frequencies above 30 Hz, the low frequency vibrations are not restrained or attenuated satisfactorily. Therefore, the elastic block structures cannot meet both requirements, that is, restraining the low frequency vibrations within the vibration restrained domain and insulating the high frequency vibrations within the vibration insulated domain.